Utility provided by the John the Ripper project to obtain the traditional Unix password file if the system uses shadow passwords.
unshadow password-file shadow-file
This manual page documents briefly the unshadow command, which is part of the john package. This manual page was written for the Debian GNU/Linux distribution because the original program does not have a manual page. john, better known as John the Ripper, is a tool to find weak passwords of users in a server.
The unshadow tool combines the passwd and shadow files so John can use them. You might need this since if you only used your shadow file, the GECOS information wouldn't be used by the "single crack" mode, and also you wouldn't be able to use the '-shells' option. On a normal system you'll need to run unshadow as root to be able to read the shadow file.
john(8), mailer(8), unafs(8), unique(8). The programs are documented fully by John's documentation, which should be available in /usr/share/doc/john or other location, depending on your system.
This manual page was written by Jordi Mallach <firstname.lastname@example.org>, for the Debian GNU/Linux system (but may be used by others).
John the Ripper and mailer were written by Solar Designer <email@example.com>. The complete list of contributors can be found in the CREDITS file in the documentation directory.